NAME

sys/time.h - time types

SYNOPSIS

^[XSI] #include <sys/time.h>

DESCRIPTION

The <sys/time.h> header shall define the timeval structure that includes at least the following members:

time_t         tv_sec      Seconds. 
suseconds_t    tv_usec     Microseconds. 

The <sys/time.h> header shall define the itimerval structure that includes at least the following members:

struct timeval it_interval Timer interval. 
struct timeval it_value    Current value. 

The time_t and suseconds_t types shall be defined as described in <sys/types.h>.

The fd_set type shall be defined as described in <sys/select.h> .

The <sys/time.h> header shall define the following values for the which argument of getitimer() and setitimer():

ITIMER_REAL

Decrements in real time.

ITIMER_VIRTUAL

Decrements in process virtual time.

ITIMER_PROF

Decrements both in process virtual time and when the system is running on behalf of the process.

The following shall be defined as described in <sys/select.h> : FD_CLR() FD_ISSET() FD_SET() FD_ZERO() FD_SETSIZE

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

int   getitimer(int, struct itimerval *);
int   gettimeofday(struct timeval *restrict, void *restrict);
int   select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
          struct timeval *restrict);
int   setitimer(int, const struct itimerval *restrict,
          struct itimerval *restrict);
int   utimes(const char *, const struct timeval [2]); (LEGACY )

Inclusion of the <sys/time.h> header may make visible all symbols from the <sys/select.h> header.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

<sys/select.h>, <sys/types.h>, the System Interfaces volume of IEEE Std 1003.1-2001, getitimer(), gettimeofday(), select(), setitimer()

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

The type of tv_usec is changed from long to suseconds_t.

Issue 6

The restrict keyword is added to the prototypes for gettimeofday(), select(), and setitimer().

The note is added that inclusion of this header may also make symbols visible from <sys/select.h>.

The utimes() function is marked LEGACY.